The BepiColombo Mercury Transfer Module has completed its final major test inside ESA’s Large Space Simulator, proving it will be able to withstand the temperature extremes it will experience on its journey to Mercury.

On the one hand, the mission will be exposed to the cold vacuum of space. On the other, it will travel close to the Sun, receiving 10 times the solar energy than we do on Earth. This translates to about 11 kW per sq m at Mercury, with the spacecraft expected to endure heating to about 350ºC, similar to a pizza oven.

Inside the simulator, the largest of its kind in Europe at 15m high and 10m wide, pumps create a vacuum a billion times lower than standard sea-level atmosphere, while the chamber’s walls are lined with tubes pumped with liquid nitrogen to create low temperatures of about –180ºC. At the same time, a set of 25kW IMAX projector-class lamps are used with mirrors to focus light onto the craft to generate the highest temperatures.

During the latest tests, carried out between 24 November and 4 December 2017, the module was rotated through 13º either side to monitor the heating and distribution. The ion engines were also activated – without creating thrust from an ion beam given the confines of the test chamber – to confirm that the module's electric propulsion system can operate in this challenging environment

The module is seen here stacked on a replica interface to mimic the science orbiters that it will be attached to during launch and the 7.2 year journey to Mercury. The four ion thrusters are seen on the top of module in this orientation. Not present in this test, the module will also be equipped with two solar wings that will unfold to a span of 30 m.

The transfer module’s job is to carry ESA’s Mercury Planetary Orbiter and Japan’s Mercury Magnetospheric Orbiter to the planet, where they will separate and enter their respective orbits. The craft will use a combination of gravity assist flybys at Earth, Venus and Mercury along with the transfer module’s ion thrusters to reach its destination.

The module will now be checked before the entire assembly is shipped to Europe’s Spaceport in Kourou, French Guiana next year. With this last major test complete, the mission is on track to be launched in the two-month window opening on 5 October 2018.

Europe’s first mission to Mercury will soon be ready for shipping to the spaceport to begin final preparations for launch.

The mission passed a major review yesterday, meaning that the three BepiColombo spacecraft, along with ground equipment and mission experts, are confirmed to start the move from ESA’s centre in the Netherlands to Europe’s Spaceport in Kourou, French Guiana at the end of next month. The launch window is open from 5 October until 29 November.

On 6 March 2018, the BepiColombo engineering model was delivered to ESA’s mission control centre in Darmstadt, Germany.

BepiColombo – ESA’s first mission to Mercury – is based on two spacecraft: the ESA-led Mercury Planetary Orbiter, with 11 experiments and instruments, and the Japanese space agency-led Mercury Magnetospheric Orbiter, carrying five experiments and instruments.

The engineering model delivered to Darmstadt comprises a 3D mock-up of the ESA module, plus a ‘flat-sat’ mock-up of the transfer module, which ties the ESA and Japanese modules together during their cruise to Mercury.

In this photo, Airbus technician Stanislaw Ballardt looks out from inside the ESA module during installation work on 7 March.

The engineering model is an electrically faithful replication of the most critical elements of the spacecraft’s main platform and flight control systems, such as its computers, mass memory and power systems.

Flight controllers will use the model throughout the mission to check software and procedures before uploading them to the real spacecraft. They will also train for flight events such as firing the electric thrusters, swinging by planets and separating the modules.